My parents (father) took out a reverse mortgage approximately 5 years ago and have accrued about $160k in total. 

Just out of curiosity, what is your reason for wanting to buy down the rate?

That kind of curiosity only grew with age and, to keep a long story short, I became engrossed in the idea of passive income and financial freedom through buy-and-hold rental properties.

If it involves carrying out the hands-off buy-and-hold investing model largely espoused by this website, where you but a bunch of leveraged properites, hire a property manager to take your worries away, and slowly watch the returns accrue, well, that's the dream Clayton Morris sold and people with even minimal experience in C and D property classes understand it tends not to work so well down in the lower end of the rental spectrum.If you're talking about being the kind of landlord I am, well, you're going to be fixing a lot of stuff yourself, waiting for a lot of people to show up who don't, dealing personally with tenants who have real problems, and most definitely not living any sort of aspirational life most people would want.To just give you a taste of this life, right now, a local buddy of mine who is also in the business is in the hospital.

Again this is typically the ranges I use/recommend  and worst case scenario if you over compensate for some expenses you'll start to accrue large operating accounts, which is way better than finding yourself cash poor. 

Out of curiosity, how much debt is too much in your opinion.

So out of curiosity, what would you say is the ONE main reason that led to you loosing it all a few years back ?

@Scott HurstEither what you have been told is entirely wrong, or being taken very much out of context.If your IRA owns rental property all cash, there are no taxes on the income, which all accrue to the IRA tax-sheltered. 

Just out of curiosity why wont you touch Boston anymore?  

First, do you know how far behind he is and how much money it would take to not only cure his default, plus any late fees and additional accrued interest?